Frequently, when one installs sheetrock in new installations, a textured surface is the preferred treatment for finishing the sheetrock immediately prior to painting. One reason for textured surfaces involves the surface characteristics which attend the use of sheetrock. Typically, adjacent panels of sheetrock must be taped, skimmed and then sanded for a smooth contour. When a wall does not receive a textured treatment, surface imperfections are readily noticeable. By providing a textured surface on the wall, the pattern of texture not only provides an interesting variegated contour, but hides surface blemishes that would otherwise be noticeable upon the finished and painted sheetrock.
On new installations, the application of texture on a sheetrock surface is at best an imprecise art. Typically, an open hopper, loaded with cementitious material in a slurry form, power feeds the cementitious material down to a spray nozzle using an impeller pump all of which is held by the operator. The broadcast pattern is extremely wide on new texturing installations and particulate matter provides a fine mist in the air which will contact all surfaces in the room being treated by the textured material. Of course, during new construction, this is not objectionable so long as the texturing process occurs at the appropriate time during construction i.e. prior to any finish work such as carpet laying, fixtures installation, glass installation has occurred. Otherwise, the textured material is sure to contact all surfaces within the environment.
A separate problem exists when texturing is required to be performed for touchup. This typically occurs when parts of the sheetrock panel need to be modified typically after all other finish work has been done. The known technique of using a wide broadcast pattern is therefore not ideal in this environment, and a noticeable blemish will have been evidenced by even an untrained eye when attempting to provide a textured patch on a given surface. Gravity fed systems magnify these problems for touch-up work.
To date, the prior art is woefully silent in mechanisms which address the problem associated with texture touchups. The following patents reflect the state of the art of which applicant is aware and is intended to discharge applicant's acknowledged duty to disclose known prior art. However, it is stipulated that none of these citations when considered singly nor when combined in any permissible manner teach or render obvious the nexus of applicant's invention particularly as set forth hereinbelow and claimed.
______________________________________ INVENTOR U.S. Pat. No. ISSUE DATE ______________________________________ McManamna, G. P. 1,704,623 March 5, 1929 Wagner, W. 3,780,910 December 25, 1973 Rudolph, R. L. 4,174,068 November 13, 1979 Ornsteen, R. L. 4,215,802 August 5, 1980 Kuminecz et al 5,519,545 May 28, 1985 Deysson et al 4,859,121 August 22, 1989 ______________________________________
The patent to McManamna teaches the use of an air-driven piston discharging a liquid into a form of air-driven nozzle. It uses two separate systems of air with numerous valves.
The device is similar to the instant invention in that an air-driven piston injects liquid into a nozzle where a separate compressed air source creates a spray. However, many differences are also apparent. No valve exists regulating liquid flow. Also the method and structure by which the instant invention is refilled is substantially different from McManamna.
The patent to Deysson et al. teaches the use of an apparatus for spraying ultrafine powders using two compressed air sources. One drives a piston within the particle-filled chamber and the other enters the chamber to suspend and eject the powder as a particle spray.
The broad concept of Deysson is similar to the invention, in that a dual air flow performs a piston driving function and a spray ejecting function. The structure of this patent is quite different however. The spraying means is substantially dissimilar because no air flow or particle flow regulating valves are included, and no refill apparatus is defined.
The Rudolph patent teaches the use of a disposable cartridge driven by air pressure in the nozzle only, providing a liquid spray. It shares only coincidental similarity with a few components of the instant invention.
The remaining references show the state of the art further. The instant invention appears to be the only device with a valve regulating fluid flow, and the concommitant method and structure for refilling the chamber appears patentably distinguishable over the prior art.